Flexible sleeve syringe and system

ABSTRACT

A syringe having an elastic sleeve which defines a fluid chamber, and a plunger positioned within the elastic sleeve. The outer diameter of the plunger is greater than the inner diameter of the elastic sleeve such that the plunger elastically deforms the sleeve during use. A syringe pump system is also provided.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 60/516,459 which was filed on Nov. 3, 2003, and isincorporated herein by way of reference.

TECHNICAL FIELD

The present invention relates to syringes and, more particularly, tosyringes having flexible components, including a flexible sleeve, thatare adapted to maintain sealing and performance integrity under varyingchemical, temperature, fatigue and pressure conditions.

BACKGROUND OF THE INVENTION

Syringes have long been used in various applications requiring precise,sterile or convenient pumping, extraction or delivery of liquids. As aresult, many varieties of syringes exist in different forms suitable fordifferent purposes.

In environments requiring precision and sterile handling of liquids formedical or industrial applications, it is necessary for syringes andtheir components to have high temperature and chemical resistance. Suchapplications may require high volume, continuous operation which,therefore, calls for designs and components capable of high cycle orfatigue resistance.

It is known to use syringes or syringe pumps having a glass sleeve and aPTFE (polytetrafluoroethylene) plunger, in which both materials areselected for their inert properties and high chemical and temperatureresistance. A problem associated with such designs, however, is tendencyfor the PTFE plunger to set, particularly after a high number of cycles.The setting of the plunger, as a result of compressive forces from theliquid pumped and the rigid glass sleeve during use, causes leakagebetween the plunger and the sleeve.

One known solution to the problems associated with glass and PTFEsystems is to over-size the PTFE plunger so that it is under greatercompressive force when installed in the glass sleeve. This solution hasdrawbacks in that the onset of leakage is merely prolonged and thesyringe will require more axial force to pump the liquid. Therequirement of more axial force will subject associated components togreater wear and higher costs in design to handle the increased load. Insituations where pumping through the syringe is continuous or highvolume, the need for increased axial force will increase power inputrequirements and associated costs.

SUMMARY OF THE PRESENT INVENTION

Some embodiments of the present invention provide a syringe or syringepump system that has superior resistance to leakage, chemicals, andheat, such as in high volume or continuous cycle environments, whilealso having low pumping force requirements.

The present invention is directed to a syringe and syringe pump systemhaving a plunger and an elastic sleeve, wherein the sleeve and plungerare sized such that the outside diameter of the plunger is greater thanthe inside diameter of the sleeve, thereby causing elastic deformationof the sleeve during use.

One embodiment of the present invention provides a syringe, comprisingan elastic sleeve defining a fluid chamber, and a plunger positionedwithin the elastic sleeve, wherein the outer diameter of the plunger isgreater than the inner diameter of the elastic sleeve such that theplunger elastically deforms the sleeve during use. The elastic sleevemay comprise a syringe sleeve and a surrounding sleeve, wherein thefluid chamber is defined by the interior of the syringe sleeve and thesyringe sleeve is positioned within the interior of the surroundingsleeve. The surrounding sleeve may comprise an elastomeric materialwhich provides a compressive force against the outer surface of thesyringe sleeve upon deformation of the sleeve during use. The syringesleeve may comprise a semi-rigid thermoplastic material, such as afluoroplastic chosen from the groups consisting of: PTFE, PFA and FEP.The surrounding sleeve may comprise, for example, silicone.

The syringe may further comprise a housing which encloses the elasticsleeve. The housing may include a first end cap located at the proximalend of the syringe sleeve, a second end cap positioned at the distal endof the syringe sleeve, and at least one sidewall extending between theend caps (e.g., a hollow tube secured to the first and second end capssuch that an annular space is provided between the tube and the elasticsleeve). The syringe may further comprise a rod which extends distallyaway from away from the plunger, and the first end cap may include anopening through which the rod extends. The second end cap may include atleast one fluid passageway in fluid communication with the fluidchamber. The proximal end of the second end cap may include a chamber,and an insert member configured for insertion into the chamber of thesecond end cap may also be provided. The distal end of the elasticsleeve may be secured within the chamber between the wall of the chamberand the insert member.

Another embodiment of the present invention provides a syringe pumpsystem. This syringe pump system may include an elastic sleeve defininga fluid chamber, a plunger positioned within the elastic sleeve, whereinthe outer diameter of the plunger is greater than the inner diameter ofthe elastic sleeve such that the plunger elastically deforms the sleeveduring use, an intake conduit having a first check valve associatedtherewith and in fluid communication with the fluid chamber, and anoutput conduit having a second check valve associated therewith and influid communication with the fluid chamber. Fluid may be drawn into thesyringe pump through the intake conduit and the first check valve, andthereafter expelled from the syringe pump through the output conduit andthe second check valve upon reciprocation of the plunger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, partially cross-sectional illustration of asyringe system according to one embodiment of the present invention;

FIG. 2 is a schematic, partially cross-sectional illustration of asyringe according to one embodiment of the present invention;

FIG. 3 is a schematic, cross-sectional, exploded illustration of thedistal end cap and insert member of the syringe shown in FIG. 2; and

FIG. 4 is a schematic, cross-sectional illustration of the proximal endcap of the syringe shown in FIG. 2; and

FIG. 5 is a schematic, partially cross-sectional illustration of aplunger which may be used in an embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provides syringes and syringesystems which provide reduced friction between the plunger and the wallof the fluid chamber, reduced wear on components such as the plunger,and/or simplified manufacturing due to an ability to compensate formisalignment and less stringent tolerances. With respect to the reducedfriction feature, embodiments of the present invention have lowerpumping force requirements. Thus, for example, when a syringe accordingto an embodiment of the present invention is motor driven (i.e., a motorcauses reciprocal movement of the plunger), less power is needed. Infact, this can allow a single motor to drive multiple syringes.

According to embodiments of the present invention, a syringe is providedcomprising an elastic sleeve defining the fluid chamber of the syringe,and a plunger positioned within the elastic sleeve. The outer diameterof the plunger is oversized (i.e., greater than the inner diameter ofthe elastic sleeve) such that the plunger (in particular, the distalhead portion of the plunger) will elastically deform the sleeve duringuse. As used herein, this elastic deformation simply means that theportion of the elastic sleeve which is adjacent the plunger at any giventime is forced outward—thus creating a bulge in the wall of the elasticsleeve at the location of the plunger (see FIG. 2). However, becausethis deformation is elastic, as the plunger is moved axially away fromthe deformed region of the sleeve and thus no longer applies an outwardforce against the interior wall of the sleeve, the deformed region ofthe elastic sleeve will return to its original size and shape.Oversizing the plunger in this manner will also reduce the risk ofleakage (the interior walls of the elastic sleeve will essentially moldto the outer surface of the plunger). Furthermore, the materials usedfor the plunger and at least the portion of the elastic sleeve formingthe wall of the fluid chamber in some embodiments comprise materialshaving low coefficients of friction (e.g., fluoroplastics), thusproviding the friction reductions mentioned above even though theplunger is oversized.

In some embodiments, in order to provide desired properties such aschemical resistance and inertness, low coefficient of friction, reducedwear, and high temperature resistance for the portion of the sleeveproviding the fluid chamber of the syringe, while also ensuring that thesleeve is elastic (i.e., resumes its original shape when not beingdeformed by the plunger), the elastic sleeve may be formed from two ormore layers of materials having distinct properties. For example, theelastic sleeve may comprise at least one semi-rigid sleeve memberpositioned within at least one elastomeric sleeve member (i.e.,concentric to one another) such that, upon deformation of the at leastone semi-rigid sleeve member, the at least one elastomeric sleeve memberwill provide a restoring force against the semi-rigid sleeve member suchthat it is returned to its original size and shape. The term“semi-rigid” simply means that the sleeve may be readily deformed by theplunger (due to the over-sizing of the plunger), but a deformed portionof the sleeve would not fully return to its original shape without theapplication of a restoring force. In one particular embodiment of thepresent invention (e.g., FIGS. 1 and 2) a semi-rigid syringe sleeve issurrounded by an elastomeric surrounding sleeve (with the surroundingsleeve sized to fit snugly over the syringe sleeve). The elastomericsurrounding sleeve provides the necessary restoring force since it isdeformed with the syringe sleeve yet has the necessary elasticproperties to force the syringe sleeve back to its orginal shape.

A syringe system 10 according to one embodiment of the present inventionis diagrammatically shown in partial cross-section in FIG. 1. A plunger12 having a rod 14 which may be attached to the plunger or formedintegrally therewith is movably coupled to a drive system 16 of any oneof the type generally known to those skilled in the art in order toimpart linear, reciprocal motion to the plunger 12 as indicated by thearrow 18. In the embodiment of FIG. 1, plunger 12 has a round profilewhen viewed from the top (not shown), though it could vary among avariety of geometrical configurations (see, e.g., FIG. 5).

A syringe sleeve 20 is shaped cylindrically to cooperate in sealingengagement with the plunger 12 which is positioned therein. However,sleeve 20 may be configured in any geometrical shape that cooperateswith the plunger 12 for sealing engagement, though in the embodimentshown it has a round cross-section. The lateral dimension or innerdiameter of the sleeve 20 is smaller than the lateral dimension or outerdiameter of the plunger 12 in order to provide a compressive fit whenthe plunger 12 is positioned inside the sleeve 20.

By way of example, the plunger 12, may be made from a variety ofmaterials such as PCTFE (polychlorotrifluoroethylene, e.g., Kel-F®) oranother suitable plastic with similar properties relating to chemical.temperature and fatigue resistance, as well as resiliency,impermeability, and chemical inertness (e.g., other fluoroplastics).While a more rigid material may be used for plunger 12, including glassor metal, such rigid materials would cause greater wear on the sleeve20. The selection of a fluoroplastic such as PCTFE provides anappropriate balance of strength, smoothness and limited elasticity.Depending on a particular application and its parameters, as well as theselection of material and dimension for the sleeve 20, another materialmay be selected for plunger 12, such as various thermoplastics (e.g.,fluoroplastics such as PTFE, FEP, or PFA. As is known to those skilledin the art, it may also be desirable to avoid the use of an indenticalmaterial for plunger 12 and sleeve 20.

By way of example, the sleeve 20 may be made from PTFE (Teflon®, forexample) or another fluoroplastic, as fluoroplastics have high chemicaland temperature resistance in addition to some elasticity.Fluoroplastics also have extremely low coefficients of friction—anadvantageous property since, among other things, it will reduce theforce required to reciprocate the plunger. Other suitable fluoroplasticsinclude PFA (perfluoroalkoxy resin), and FEP. Sleeve 20 can comprise anextruded, thin-walled polymer tube.

The combination of materials used for the sleeve 20 and plunger 12provides minimal frictional resistance in combination with sufficientsealing capability during pumping of a liquid.

The syringe chamber 22 is in fluid communication with an intake conduit24 having a check valve 26, and an output conduit 28 having a checkvalve 30 (such fluid communication may be provided within end cap 36described further herein). Of course any number and type of fluidoutlets, conduits, valves, and connector elements may be provided. Forexample, the check valves could be replaced by one or more multi-portselection valves (e.g., a rotary selection valve), thus providing asyringe system for selectively delivering and/or extracting fluid byoperation of the selection valve(s) and a drive system whichreciprocates the plunger. In the embodiment shown in FIG. 1, the syringesystem 10 is essentially a positive displacement pump which is operatedmerely by reciprocating plunger 12 (e.g., manually or using a drivesystem 16 which causes reciprocal movement of plunger rod 14 and henceplunger 12 within syringe sleeve 20.

As also shown in FIG. 1, a silicone sleeve 32 surrounds the syringesleeve 20. Of course silicone is merely exemplary, as other elastomericmaterials with sufficient elasticity and restoring energy for restoringsyringe sleeve 20 may be used for the surrounding sleeve 32. A housingcomprises a lower end cap 34, having an opening 36 and seals 38 for therod 14 and other components; an upper end cap 36 cooperating withvarious seals 38 as shown; and a set of sidewalls 40. The sidewalls 40may comprise of any number such as four, that encloses the othercomponents and supports the end caps 34 and 36 or a single cylindricalsidewall (not shown) may be used. The seals 38 may be O-rings or otherseals, including seal assemblies of the type known to those skilled inthe art. The various components may also be affixed to one another usingand adhesive (e.g., an epoxy glue), heat welding, ultrasonic welding,snap-fitttin, or other suitable means known to those skilled in the art.The gap 42 between the sidewalls 40 and the silicone sleeve 32 may befiled with a compressible medium such as, but not limited to, gel,liquid, air, or foam, in order to provide additional support to thesurrounding sleeve 32 and the syringe sleeve 20. The drive mechanism 16may have any one of various types of internal gearing such as rack andpinion and it may be adapted to simultaneously drive two or more syringepumps made in accordance with the present invention and mounted to abench or freestanding work station.

FIGS. 2-4 depict another embodiment of a syringe 110 according to thepresent invention. Syringe 110 once again includes a fluid chamber 122defined by the interior of a flexible sleeve which is elasticallydeformed by plunger 112 during use (i.e., as plunger 112 moves in eitheror both of the directions indicated by arrow 118).

Plunger 112 can have any of a variety of shapes and configurations, andthat shown in FIG. 2 is merely exemplary. FIG. 5 depicts an alternativeembodiment for a plunger 212 and a plunger rod 214 attached thereto.Plunger 112 can be made from any of a variety of materials, particularlythermoplastics such as fluoroplastics. Exemplary materials include PTFE,PCTFE (e.g., Kel-F®), FEP and PFA.

As also seen in FIG. 2, a plunger rod 114 is attached to, and extendsaway from the proximal end of plunger 112. Plunger rod 114 may onceagain be attached to any suitable drive system 116, or may even beconfigured for manual use (e.g., by providing a handle or other deviceat the proximal end of plunger rod 114 in order to facilitate manual useof syringe 110). Plunger rod 114 may be made from any of a variety ofmaterials, particularly rigid materials such as stainless steel.

Syringe 110 shown in FIG. 2 also includes a flexible, elastic sleevewhich is elastically deformed by plunger 112, as shown in FIG. 2. (Itshould be noted that the thickness of the elastic sleeve components andthe outer housing 140 in FIG. 2 have been exaggerated to more clearlydepict the deformation of the elastic sleeve). The outer diameter ofplunger 112 is greater than the inner diameter of the flexible sleeve ofsyringe 110 such that plunger 112 will urge the adjacent region of theelastic sleeve outwardly. Thus, the flexible sleeve will bulge outwardlyin the region adjacent plunger 112, and the bulge thus created willtravel along the sleeve as plunger 12 is moved in the directions shownby arrow 118. As the plunger moves away from a deformed region of theelastic sleeve, that region will return to its original size and shape,this ensuring a fluid tight fit between the plunger and the elasticsleeve even after repeated use of the syringe. While the elastic sleeveof syringe 110 may comprise a single, sleeve element, the embodiment ofFIG. 2 once again includes a pair of sleeves which provide the elasticsleeve member of syringe 110.

In particular, syringe 110 includes a syringe sleeve 120 and anelastomeric surrounding sleeve 132 which surrounds syringe sleeve 120.Syringe sleeve 120 may be made from a thermoplastic material, such as afluoroplastic. Exemplary materials include PTFE, FEP and PFA, all ofwhich provide reduced friction, thereby minimizing the force needed tomove plunger 112, as well as chemical resistance and inertness. Thematerial used for syringe sleeve 120 may also provide a sleeve 120 whichis semi-rigid so that sleeve 120 may be deformed by plunger 112, asshown. In the embodiment shown, syringe sleeve 120 is not itself formedfrom an elastomeric material, since elastomers tend to have lesschemical resistance than thermoplastics such as PTFE, FEP or PFA. Itshould be pointed out that fluoroplastics (e.g., PTFE, FEP and PFA) andthe like do have some elasticity, particularly when extruded into athin-walled tube which is then deformed in the manner shown in FIG. 2.However, these materials will take a set (due to creep or coldflow)—meaning that they will not fully return to their original size andshape without the application of a restoring force. Therefore, in orderto ensure that the walls of syringe sleeve 120 return to their originalinside diameter after passage of plunger 112, elastomeric sleeve 132surrounds syringe sleeve 120 such that elastomeric sleeve 132 will urgesyringe sleeve 120 back to its original size and shape. Elastomericsleeve 132 will be deformed in the region adjacent plunger 112, asshown, since it is formed from an elastomer. However, the deformedregion of elastomeric sleeve 132 will return to its original shape onceplunger 112 has moved to a new location (i.e., plunger 112 is no longerapplying an outward force to the previously-deformed region). Because ofthis, sleeve 132 will also urge syringe sleeve 120 back to its originalsize and shape, thus ensuring a fluid-tight fit between plunger 112 andsyringe sleeve 120, even after repeated use.

Syringe 110 shown in FIGS. 2-4 also includes a pair of end caps, namelyproximal (or first) end cap 134 and distal (or second) end cap 136.Syringe sleeve 120 extends between end caps 134 and 136, as shown.Plunger rod 114 extends through a central bore 135 provided on proximalend cap 134, as shown in FIGS. 2 and 4. However, in this embodiment,central bore 135 is approximately equivalent in size to the outerdiameter of syringe sleeve 120 such that plunger rod 114 will notcontact bore 135 of proximal end cap 134. In this manner, plunger rod114 is free to float with respect to proximal end cap 134. This not onlysimplifies manufacturing and assembly, but also eliminates the need forprecise alignment of plunger rod 114 and drive system 116. In addition,this arrangement also reduces the force required to reciprocate plunger112 since there is no frictional contact between plunger rod 114 and anycomponent of syringe 110.

As best seen in FIG. 4, proximal end cap 134 essentially comprises acylindrical ring having a shoulder 147 extending around the outercircumference thereof. As further discussed herein, the size (or depth)of shoulder 147 may be approximately equivalent to the wall thickness ofouter sidewall (or tube) 140, such that outer tube 140 may be secured toproximal end cap 134 and abut against shoulder 147, thus providing asmooth transition between end cap 134 and outer tube 140 (see FIG. 2).As also seen in FIG. 2, the proximal end of syringe sleeve 120 may besecured to the interior wall of end cap 134, such as by use of anadhesive, heat welding, ultrasonic welding, snap fitting, or other knownor suitable attachment means. However, in some embodiments, it may notbe necessary to attach syringe sleeve 120 to end cap 134. Tube 140 maysimilarly be attached to the end caps by means of an adhesive (e.g.,epoxy), heat welding, ultrasonic welding, snap fitting, or other knownor suitable attachment means.

Syringe 110 also includes a distal end cap 136, as best seen in FIGS. 2and 3. Like end cap 134, distal end cap 136 can be made from any of avariety of materials, particularly various types of thermoplastics. Inthe embodiment of FIG. 2, there is generally no fluid contact with endcaps 134 and 136. Therefore, chemical resistance is not as significantof a factor with respect to these two components. One suitable materialfor end caps 134 and 136 is PEEK.

As best seen in FIG. 3, distal end cap 136 includes a hollow,cylindrical body 137 and a connection member 139 extending away from thedistal end of body member 137. In the embodiment shown, connectionmember 139 merely comprises a hollow cylinder having a centralpassageway (or bore) 146 extending therethrough. However, connectionmember 139 may have any of a variety of shapes and configurations, andmay be configured in order to facilitate attachment of the syringe to avariety of devices. For example, connection member 139 may alternativelycomprise a male or female-threaded connector, a Luer connector, or anyof a variety of other connecting elements known to those skilled in theart. A quick disconnect fitting may also be attached at the distal endof connection member 139 in order to facilitate attachment of syringe110 to a valve structure, or other apparatus or device. It is evencontemplated that a hypodermic needle may be attached to connectionmember 139 (particularly when connection member 139 comprises a Luerconnector), thus allowing the syringe to be used for the injection orwithdrawal of fluids from a patient and other similar uses.

Like end cap 134, cylindrical body 137 of distal end cap 136 includes ashoulder (or flange) 143 which extends about the outer circumference ofbody 137. Once again the depth of shoulder 143 may be approximately thesame as the wall thickness of outer tube 140, and outer tube 140 may beattached to end cap 136 such that the distal end of outer tube 140 abutsagainst shoulder 143, as shown. Outer tube 140 may be attached to endcap 136 in the same manner as described previously.

As mentioned previously, cylindrical body member 137 is generally hollowin nature, thus providing a chamber 145 at the proximal end of end cap136. The distal end of syringe sleeve 120 may be inserted into chamber145. In order to ensure a fluid-tight connection between syringe sleeve120 and end cap 136, an insert member 150 is also provided. Insert 150includes a first cylindrical portion 151 and a second cylindricalportion 152 extending away from the distal end wall 153 of firstcylindrical portion 151. A bore 155 extends through both first andsecond cylindrical portions 151 and 152. During assembly, the distal endof syringe sleeve 120 is inserted into chamber 145 of body member 137 ofdistal end cap 136, and thereafter insert 150 is inserted into chamber145 such that second cylindrical portion 152 extends through bore 146 onend cap 136 and first cylindrical portion 151 is positioned withinchamber 145. The distal end wall of silicone sleeve 120 will thus bepositioned within chamber 145, between the outer circumferential surfaceof first cylindrical portion 151 of insert 150 and the interior sidewallof chamber 145. In addition, chamber 145 and insert 150 may be sized andconfigured such that distal end wall of syringe sleeve 120 will becompressed between chamber 145 and the outer circumferential surface offirst cylindrical portion 151 of insert 150 in order to secure syringesleeve 120 to end cap 136.

In the embodiment shown in FIG. 3, a ridge 144 extends around the innercircumference of the proximal end of chamber 145 of end cap 136. Thedistal end of syringe sleeve 120 is folded outwardly down over the outersurface of syringe sleeve 120, as best seen in FIG. 2. The foldedportion of syringe sleeve 120 is positioned within the interior of bodyportion 137, distally of ridge 144. The height of ridge 144 is such thatonce the distal end of sleeve 120 is inserted into end cap 136 andinsert 150 has been secured to end cap 136 as shown in FIG. 2, ridge 144will ensure that the distal end of syringe sleeve 120 remains within theinterior of end cap 136, secured between insert 150 and the interiorsidewall of chamber 145. In fact, once insert 150 has been secured toend cap 136, it may not be necessary to bond or otherwise secure syringesleeve 120 to either end cap 136 or insert 150. For example, insertmember 150 may be press or snap-fit into end cap 136 (e.g., byappropriate sizing of cylindrical portion 152 with respect to bore 146on end cap 136. Alternatively, insert member 150 may be adhesivelybonded to end cap 136 or attached via heat welding, ultrasonic welding,or other attachment means. It is also contemplated that insert member150, end cap 136 and the distal end portion of syringe sleeve 120 may beattached to one another in the same manner (e.g., by use of an adhesiveapplied within chamber 145 and, if desired within bore 146.

Since insert 150 will be in fluid contact, it will often be desirable tomanufacturer insert 150 from a chemically-resistant and inert material.Such materials include any of a variety of thermoplastics, such asfluoroplastics, including PTFE, FEP, PCTFE or PFA.

As mentioned previously, syringe 110 also includes an outer tube 140.Outer tube 140 may simply comprise a clear plastic tube, and isprincipally intended to protect the flexible sleeve and plungercomponents of syringe 110 and provide an aesthetically pleasingappearance. Visible indicia may be provided on tube 150 in order tofacilitate use of syringe 110, such as measurement lines imprinted on ormolded into tube 140. Since the materials used to manufacturer theflexible sleeve components (i.e., syringe sleeve 120 and elastomericsleeve 130) will often not provide a clear view of fluid chamber 122 andthe position of plunger 112, measurement lines and the like may notnecessarily provide a precise indication of fluid volume within syringe110. However, the bulge in the flexible sleeve caused by plunger 112will generally be visible through tube 140. One exemplary material fortube 140 is commercial grade acrylic resin, however, any of a variety ofmaterials may be employed.

As also seen in FIG. 2, elastomeric sleeve 132 is shorter in length thansyringe sleeve 120. In fact, once assembled, elastomeric sleeve 132encircles syringe sleeve 120 and only extends between end caps 134 and136. Elastomeric sleeve 132 may be made from any of a variety ofelastomeric materials. In general, the composition and wall thickness ofelastomeric sleeve 132 should be such that it provides sufficientcompressive force against the exterior wall of syringe sleeve 120 inorder to return syringe sleeve 120 to its original size and shape afterpassage of plunger 112 (i.e., to return a deformed region of sleeve 120to its original size and shape once that deformed region is no longadjacent plunger 112). One particularly suitable material is silicone.In general, the inner diameter of elastomeric sleeve 132 may be equal toor slightly less than the outer diameter of syringe sleeve 120, thus notonly ensuring that elastomeric sleeve 132 remains in place on syringesleeve 120 (provides a snug fit), but also ensuring that elastomericsleeve 132 will be able to fully restore syringe sleeve 120 to itsoriginal size and shape in regions to which plunger 112 is not adjacent.

As with the previous embodiment, the outer diameter of plunger 112(defined as the maximum outer diameter of any portion of the plunger,particularly when non-cylindrical plungers such as plunger 212 in FIG. 5are employed) is greater than the interior diameter of syringe sleeve120. The difference in diameter should be sufficient to ensure afluid-tight seal between the plunger and the syringe sleeve, to causedeformation of the syringe sleeve wall adjacent the location of theplunger, and allow the plunger to freely slide within the syringe sleevewith minimal force. In one exemplary embodiment, and by way of exampleonly, a PTFE plunger 112 having an outer diameter of 0.578 inches may beemployed with a cylindrical syringe sleeve made from FEP having an innerdiameter of 0.575 inches and a wall thickness of 0.012 inches. In suchan embodiment, the elastomeric sleeve may be a cylindrical siliconesleeve having an inner diameter of 0.599 inches and a wall thickness of0.015 inches.

In some embodiments of the present invention, the elastic sleeve may beformed from one or more thin-walled tubes. In the case of the syringesleeve, it may comprise an extruded, thin-walled thermoplastic tube,such as a fluoroplastic tube (e.g., PTFEF, FEP or PFA). By way ofexample, the wall thickness for the syringe sleeve may be between about0.008 and about 0.062 inches. In the case of the surrounding sleeve(e.g., a thin-walled silicone tube) the wall thickness may be betweenabout 0.008 and about 0.125 inches.

The embodiments described herein may used for a variety of tasks suchas, but not limited to, metering, pumping in product mixing orpackaging, and controlling flow in laboratory environments.

While the various embodiments of the present invention have been hereindescribed, it is understood that various modifications can be madewithout departing from the scope of the invention.

1. A syringe, comprising: (a) an elastic sleeve defining a fluidchamber; and (b) a plunger positioned within said elastic sleeve,wherein the outer diameter of said plunger is greater than the innerdiameter of said elastic sleeve such that said plunger elasticallydeforms said sleeve during use.
 2. The syringe of claim 1, wherein saidelastic sleeve comprises at least one semi-rigid sleeve memberpositioned within at least one elastomeric sleeve member such that, upondeformation of said elastic sleeve, said at least one elastomeric sleevemember will provide a restoring force against the semi-rigid sleevemember such that said at least one semi-rigid sleeve member will bereturned to its original size and shape
 3. The syringe of claim 1,wherein said elastic sleeve comprising a syringe sleeve and asurrounding sleeve, wherein said fluid chamber is defined by theinterior of said syringe sleeve and said syringe sleeve is positionedwithin the interior of said surrounding sleeve.
 4. The syringe of claim3, wherein said surrounding sleeve comprises an elastomeric sleeve whichprovides a compressive force against the outer surface of said syringesleeve upon deformation of said sleeve during use.
 5. The syringe ofclaim 4, wherein said syringe sleeve comprises a semi-rigidthermoplastic material.
 6. The syringe of claim 5, wherein said syringesleeve comprises a fluoroplastic chosen from the groups consisting of:PTFE, PFA and FEP.
 7. The syringe of claim 4, wherein said surroundingsleeve comprises silicone.
 8. The syringe of claim 1, further comprisinga housing which encloses said elastic sleeve.
 9. The syringe of claim 8,wherein said housing comprises a first end cap located at the proximalend of said syringe sleeve, a second end cap positioned at the distalend of said syringe sleeve, and at least one sidewall extending betweensaid end caps.
 10. The syringe of claim 9, further comprising a rodwhich extends distally away from away from said plunger, and furtherwherein said first end cap has an opening through which said rodextends, and further wherein said second end cap has at least one fluidpassageway in fluid communication with said fluid chamber.
 11. Thesyringe of claim 9, wherein said at least one sidewall comprises a tubesecured to said first and second end caps such that an annular space isprovided between said tube and said elastic sleeve.
 12. The syringe ofclaim 11, wherein the proximal end of said second end cap includes achamber and further comprising an insert member configured for insertioninto said chamber of said second end cap, and further wherein the distalend of said elastic sleeve is secured within said chamber between thewall of said chamber and said insert member.
 13. A syringe pump system,comprising: (a) an elastic sleeve defining a fluid chamber; (b) aplunger positioned within said elastic sleeve, wherein the outerdiameter of said plunger is greater than the inner diameter of saidelastic sleeve such that said plunger elastically deforms said sleeveduring use; (c) an intake conduit having a first check valve associatedtherewith and in fluid communication with said fluid chamber; and (d) anoutput conduit having a second check valve associated therewith and influid communication with said fluid chamber; wherein a fluid may bedrawn into the syringe pump through said intake conduit and said firstcheck valve, and thereafter expelled from said syringe pump through saidoutput conduit and said second check valve upon reciprocation of saidplunger.